Common misconceptions › Class 11 › Physics › Oscillations Class 11 Physics · Chapter 13 · NCERT (keph206)
Oscillations: common misconceptions
See the tempting mistake students make in Oscillations, why it feels right at first glance, and a worked visual example that shows the right idea.
Worked visual “If your child says…” (8) Teach & practice The tempting mistake & worked visual Where does a spring mass move fastest? Wrong
The mass moves fastest at maximum stretch because the spring pulls hardest there.
Why it feels right. I connect the biggest force with the biggest speed.
Right
The mass changes direction at maximum displacement. In ideal spring motion its speed peaks at equilibrium.
Worked example
Left end Equilibrium Right end Speed 0 Fastest Speed 0 The mass is momentarily at rest at both ends. Its speed is greatest as it crosses equilibrium. Release a mass from maximum stretch. It starts at rest. At equilibrium, spring potential energy is at a minimum and speed is at a maximum. The mass then slows to rest at the opposite end. If your child says… (8 concept checks in this chapter)
As you work through Oscillations , listen for these everyday misunderstandings and use the prompt alongside each one.
If your child says…
“It has returned to the centre, so the cycle is finished.”
Ask together Is the spoon travelling the same way on these two centre crossings? What’s true Passing the centre in the opposite direction does not complete a cycle. If your child says…
“The starting position tells us the phase.”
Ask together Do these matching projection positions have matching directions? What’s true Between the ends, the same position occurs at different phases when travelling in opposite directions. If your child says…
“When it stops at an end, its acceleration is zero.”
Ask together Where is the acceleration curve when the velocity curve starts at zero? What’s true At either end, speed is zero but acceleration has its greatest magnitude, directed towards equilibrium. If your child says…
“Any force pulling back gives exact SHM.”
Ask together Would a force growing eightfold when displacement doubles satisfy that requirement? What’s true A restoring force must also vary directly with displacement for exact SHM. If your child says…
“Twice the amplitude means twice the energy.”
Ask together How much does the square of a number increase when that number doubles? What’s true For the same ideal spring, doubling amplitude requires four times the energy. If your child says…
“Four times the mass means four times the period.”
Ask together What does taking the square root do to the fourfold mass increase? What’s true On the same ideal spring, period grows with the square root of mass. If your child says…
“Four times the length means four times the period.”
Ask together What is the square root of four? What’s true At fixed gravity, small-swing period grows with the square root of length. If your child says…
“A wider cork bobs faster because water pushes harder.”
Ask together If the water pushes harder, what also makes the wider cork harder to accelerate? What’s true Wider uniform corks have unchanged ideal periods for equal heights, equal densities and small bobs. Use this chapter three ways Previous chapter Kinetic Theory Next chapter Waves
In the app, your child answers a short check-in with confidence taps, and you see which of these misunderstandings showed up—and which ones are gone.
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